For operating a video surveillance system (VSS) able to monitor a set of surveillance zones (SZ) by a set of cameras (CAM), an application server (AS) in a telecommunication network (TN) able to communicate with the video surveillance system (VSS) performs the following steps: for each mobile terminal (MT) that has established an emergency call with an emergency call center (ECC) and whose user is witness of an incident, retrieving localization data (LocD) associated with the mobile terminal (MT), determining if said mobile terminal is located in a surveillance zone (SZ), using the retrieved localization data, receiving a message (Mes) sent from the mobile terminal, the message containing current localization data (LocDc) and a direction towards the incident, and if at least two mobile terminals are located in a same surveillance zone (SZ), computing coordinates (Cdl) of the incident, taking into account said current localization data (LocDc) and said directions provided by said at least two mobile terminals, sending an incident message (Mesl) containing the coordinates (Cdl) of the incident to the video surveillance system (VSS) that is able to select at least one camera (CAM) using the coordinates of the incident.